docbookx: XML scheme for documentation1

DocBook is a widely used XML scheme for writing documentation and help.
It has a very rich markup which allows you to use XSL stylesheets to
produce various target formats such as HTML, PostScript, PDF, RTF, and
HTMLHelp. ScrollKeeper was designed with an emphasis on DocBook, since
it has the richest markup of all commonly used documentation formats
which allows ScrollKeeper to extract the most useful information from
the document itself.

The DocBook DTD and stylesheets are typically distributed in packages
which lack installation scripts. In the past, installation was simple
enough that users could easily just copy the files into place. Now that
modern XML libraries, such as libxml, support XML catalogs, correct
installation of DTD's and stylesheets require proper catalog
registration.